CEACAM5 and medullary thyroid gland carcinoma: According to the revised American thyroid association (ATA) guideline, thyroid nodules suspected for or diagnosed as MTC in cytological or histopathological examinations, respectively, should be managed with neck ultrasound examination, determinations of serum Ctn and CEA levels, and DNA analysis for the rearranged during Transfection (RET) germline mutation [5].